Most video recorders of the type intended to be used with television receivers include a system for enabling the automatic, unattended recording of programs scheduled for future transmission. In such systems the operator can load a future schedule memory with signals representing the channel, starting time and ending time (or alternatively duration) of one or more future occurring programs that it is desired to record. The system includes a real time clock and when a comparator determines that the present time has reached the starting time of a program to be recorded the tape drive is energized and the channel number stored in the memory is used to control the tuner of the video recorder. When the real time reaches the ending time of the program the recording process is terminated.
Often the source of signals for the video recorder constitutes either a cable or satellite multi-channel signal including one or more channels which are scrambled to prevent their reception by an unauthorized source. These signals must be descrambled before they can be recorded or displayed on the television receiver. Tuner/descramblers are typically employed for this purpose. Popularly called "cable boxes" these units receive the output of the cable and/or the satellite and may be tuned by the operator, typically employing an infrared remote control device, to a desired channel. The output of the channel box is provided to the video recorder and neither directly to the T.V. receiver or to the T.V. receiver via the video cassette recorder.
A variety of arrangements may be used to interconnect the tuner/descrambler, the video recorder and the T.V. receiver such as those disclosed in U.S. Pat. Nos. 4,630,133 and 4,771,456. Some of these systems allow one channel to be recorded while a different channel is displayed on the T.V. receiver.
In all of these systems the proper recording of a future scheduled television program occurring on one of the scrambled channels requires that the descrambler be tuned to the desired channel at the time of occurrence of the signal to be recorded. Often the future schedule memory is programmed a long time in advance of the time of occurrence of the program to be recorded. If the system is used for real time viewing or recording between the time of programming and the time of occurrence of the future program to be recorded, the channel selector the descrambler may have been adjusted to tune some channel other than the one that it is desired to record. The operator must then return the descrambler setting to the proper channel before recording for the system to operate properly. Particular difficulty is encountered when the schedule memory is programmed to record two future programs occurring on different scrambled channels. It is then necessary to adjust the scrambler setting after the occurrence of the first program before the occurrence of the second one.